Octillery are red cephalopod Pokémon with turret-like mouths, yellow bumps on their rock-hard heads, and yellow suction cups on each tentacle. They possess eight tentacles, two of which are used for manipulating objects while the other six don't appear to be used as much aside from a stabilizing role.

Octillery is much more powerful than its pre-evolved form, Remoraid, but it happens to be much slower. Octillery's tentacles boast stronger gripping power. Because of that, it is very hard for it to be blown away. It is also capable of using various moves that either launch projectiles or beams, such as Sludge Bomb, Flamethrower, Energy Ball, Flash Cannon, Rock Blast, Bullet Seed, Charge Beam, and due to its status as a fully evolved Pokémon, it can also use Hyper Beam and Giga Impact. Octillery is the only known Pokémon that learns Octazooka by leveling up.

Female Octillery have smaller suction cups on their tentacles. The yellow bumps on their head are also smaller. Both Octillery and Remoraid are normally found in oceans. However, they are occasionally found in freshwater lakes.

Octillery are relaxed Pokémon who love fuss from their Trainers. Wild Octillery will spurt ink at predators to protect their young from danger. Even though caught Octillery are more docile, wild Octillery can be very stubborn at times. Octillery instinctively sneak into rocky holes, and if it gets sleepy, it steals the nest of a fellow Octillery. It sometimes sprays ink on prey by sticking out only its mouth, and its suction cups hold prey tightly.